A transmission typically converts a speed input from a power source, such as an internal combustion engine, and outputs a different speed to another device that consumes the power provided, such as drive wheels for a vehicle. A hybrid power split transmission can enhance the output or store input energy for later output. Such devices often can be used to capture excess energy from the primary power source or recover energy from the power consumer, such as from braking the drive wheels of a vehicle, thereby further increasing efficiency.
Power split transmissions with both mechanical and hydraulic components generally can be categorized as either an input-coupled type, where the hydraulic system is coupled to the input, or an output-coupled type, where the hydraulic system is coupled to the output. In both types the power source typically is mechanically coupled to a power consumer, for example via a planetary gear assembly.